1. Field of the Invention
The invention generally relates to an antiglare film applicable to polarizers or screens of computers, TVs or the like, and particularly relates to a high resolution and low reflectivity antiglare film that enables a clear display.
2. Related Art
In a display with light emission, the light emitting from interior of the display has to be diffused before leaving the display surface, otherwise the light is glaring and irritant to user's eyes. Therefore, there is usually an antiglare film furnished on surface of a display for diffusing the emitting light. On the other hand, any exterior light coming to the surface of the display should also be diffused in order to prevent from reflection and causing difficulty for user to watch images on the display. So, an antiglare film for the display is desired to be functional both in diffusing the interior light and reducing reflection of the exterior light.
There are a lot of technical documents and patents relating to antiglare film. Some documents and patents on antiglare films using light-transparent fine particle coatings are described herein.
U.S. Pat. No. 5,998,013 discloses an antiglare hard coat film for diffusing exterior light. The film is coated with a layer comprising an ultraviolet-curing resin and agglomerates of colloidal silica particles formed with an amine compound. The colloidal silica particles are used to form the roughness of the surface, however, the particles with variant diameters unevenly gathered on the film surface cause insufficient visibility of the film. Especially when making a higher diffusion antiglare film with higher roughness, the clarity gets worse. Similarly, antiglare films disclosed in U.S. Pat. Nos. 6,074,741 and 6,164,785 also have the problems of less clarity for higher diffusion. Further, the prior arts do not achieve a low reflectivity property.
In order to increase diffusion rate, the prior arts use larger particles to get higher roughness. However, the higher diffusion also lowers the clarity and contrast of the image. Therefore, methods for controlling particle size or mixing different kinds of particles evenly to solve the aforesaid problems become important development issues.
Besides using the aforesaid light-transparent particles coated on a film for diffusing the exterior light, another kind of antiglare film uses particles dispersed in a resin, and diffuses the interior light by means of the different refractive indexes between the particle and the resin. For example, in U.S. Pat. No. 6,217,176, two kinds of light-transparent particles with different refractive index are contained in a light-transparent resin. So, the interior light can be diffused by the particles. The particles stacked on the film also diffuse the exterior light and improve image clarity. However, this antiglare film still lacks of a low reflectivity. Then, in U.S. Pat. No. 6,347,871, two resin coat layers having properties of diffusing interior and exterior light respectively are coated on the film. The process is more complicated due to the two layer coatings, and the antiglare film still lacks of a low reflectivity.
For the above reasons, it is required to have an antiglare film capable of diffusing interior and exterior lights for preventing glare, improving visibility, and also decreasing reflectivity of the display. Nano-grade particles are well dispersed on surface of a resin. The roughness and dispersal of particles can be controlled so as to prevent from the problems of larger particles, uneven dispersal, low clarity and low contrast of prior arts. A one-time coating and a low reflectivity are also attained.